System and method for cryogenic separation of plant material

ABSTRACT

Systems and methods for cryogenic separation of plant material are provided. A method of cryogenic separation of plant material, includes placing a sieve into a vessel. Plant material is placed in the sieve. Cryogenic fluid is provided at or below −150 degrees Celsius to the sieve. The plant material is agitated within the sieve and the vessel to separate plant particulates solidified by the cryogenic fluid from the remainder of the plant material. The cryogenic fluid and plant particulates are removed from the vessel.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.17/093,078, filed Nov. 9, 2020, which is a divisional of U.S.application Ser. No. 15/606,672, filed May 26, 2017.

BACKGROUND

This application relates in general to separating plant particulatesand, in particular, to a system and method for cryogenic separation ofplant material.

Plant components are widely popular across different industries for usein cosmetics, perfumes, drug compositions, food, crafts, and fabrics. Toobtain the necessary components, plant material must be processed toseparate those components of the plant from other parts not needed. Forinstance, many pharmaceutical companies utilize pharmacologically activeextracts that are separated from plant materials. However, separationprocesses must be carefully selected and performed to ensure purity andhigh yields of the desired component.

For example, indumentums of a plant often include the highestconcentration of certain plant compounds, which are often used in drugmanufacture. Indumentums are extremely fragile due to their resinousnature and can rupture during mechanical separation. Thus, much of thecompounds can be lost due to rupture during conventional methods forextraction, such as solvent extractions and mechanical extractions.

Solvent separations require solvents, such as hydrocarbon, alcohol, orcarbon dioxide, which can dissolve chemical components of a plant, suchthat indumentums are not physically preserved. The solvents eventuallyevaporate and only the chemical components are left together, withoutseparation from other components.

Conventional processes for mechanical separation can be performed withor without an aqueous solution. Mechanical separation performed withoutan aqueous solution, such as water, utilizes a system of screens toseparate plant components by size, but such process can cause thefragile indumentums to rupture. Mechanical separation can also require amatrix, such as water, which can alter the composition of the extractedplant component or a ratio of the desired plant components. Such processcan include separation achieved through physical agitation in a reducedtemperature aquatic matrix, followed by filtration through sequentiallayers of varied mesh, and finally drying of the separated plantcomponent.

However, due to the aqueous nature of the separation, the minimumtemperature for use in the extraction process is limited, which in turnlimits the ability to preserve any volatile compounds. Also,preservation can be inhibited by retention of the plant components inthe aqueous filtrate. Further, use of water as a solvent during theseparation process and subsequent high moisture content of the plantparticulates during and after separation can lead to waterbornepathogens, microbial growth, and other types of possible contamination.

Therefore, a need remains for a process that provides separated plantcomponents, while maintaining a consistent chemical preservation of thedesired components. Additionally, the process should be effective toresult in high yields of the desired separated component, while ensuringthat such components are sufficiently pure and free of contamination.

SUMMARY

Extraction of plant materials should be efficiently performed to preventbreakage or rupture of fragile components, such as indumentums, andensure sufficiently pure components, free of contamination. Solventextractions utilize solvents that dissolve chemical components of aplant, preventing preservations of certain components, such asindumentums, while most conventional mechanical extraction processesutilize aqueous solutions, which can lead to waterborne pathogens ormicrobial growth. Accordingly, a non-aqueous extraction process helpsprevent any contamination due to water and includes filling a vesselwith cryogenic fluid, placing one or more plants for processing into thevessel, providing agitation to the plants, and pulling the plantparticulates remaining in the vessel out, while opening a valve in thevessel to release those components separated from the matrix.

One embodiment provides a system and method for cryogenic separation ofplant material. A vessel is filled with cryogenic fluid having atemperature at or less than −150 degrees Celsius. Plant material isplaced into the vessel via a basket and agitation is provided to theplant material in the vessel for a predetermined time period. Uponcompletion of the time period, the basket having at least a portion ofthe plant material is removed from the vessel. Plant particulatesseparated from the plant material during the agitation settle to thebottom of the vessel. The vessel is drained of the cryogenic fluid,including plant particulates separated from the plant material.

Still other embodiments will become readily apparent to those skilled inthe art from the following detailed description, wherein are describedembodiments by way of illustrating the best mode contemplated. As willbe realized, other and different embodiments are possible and theembodiments' several details are capable of modifications in variousobvious respects, all without departing from their spirit and the scope.Accordingly, the drawings and detailed description are to be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a separation system for separating plantmaterial, in accordance with one embodiment.

FIG. 2 is a flow diagram showing a method for separating plant materialusing the separation system of FIG. 1 .

FIG. 3 is a side view of a different separation system for separatingplant material, in accordance with one embodiment.

DETAILED DESCRIPTION

Conventionally, some plant separation methods require the use of aqueoussolutions. However, the use of such aqueous solutions can lead tocontamination, such as waterborne pathogens and microbial growth. Toprevent contamination from occurring, a non-aqueous separation processis utilized. FIG. 1 is a side view of a separation system 10 forseparating plant material 40, in accordance with one embodiment. Theseparation system 10 includes a separation vessel 15, an agitator 20, atleast one perforated basket 17, and a collection tray 19 to collectplant particulates separated from the plant material 40. Hereinafter,the terms “particulate” and “component” are used interchangeably withthe same intended meaning, unless otherwise indicated.

The separation vessel 15 can have a conical shape with an opening on atop end that extends through a bottom end, which tapers into a stem 21with a valve 18 to regulate the flow of fluid through the vessel. Thevessel 15 can be made from material, such as food grade stainless steel,as well as other types of material. At a minimum, the material should beable to withstand extended contact with cryogenic fluids, such as thosefluids with a temperature of −150 degrees Celsius or less.

The vessel 15 can be supported and raised via three or more support legs22. The length and number of the legs 22 can be dependent on the size ofthe vessel 15 and placement of the vessel 15. For example, when thevessel 15 is sized to be placed on a table, the legs 22 will likely beshorter than when the vessel 15 is larger and must be placed on thefloor. Additionally, as the vessel size increases, the size and numberof the legs 22 can also increase. Each of the legs 22 can have a shape,such as conical or square, and include a rolling caster 23 with a lockto allow easy movement of the vessel. Other shapes of the vessel andlegs are possible.

In one embodiment, a jacket 16 can be placed over at least a portion ofthe vessel 15 to control a temperature inside the vessel 15 and preventexcessive condensation on the surface of the vessel. The vessel jacket16 can be filled with an insulator, such as foam or voided with avacuum. In one embodiment, the vacuum can range from 759 torr down to aminimum pressure rating assigned to the vessel. For example, a stainlesssteel vessel has a lower minimum pressure rating than a vessel made fromfood grade polymeric material.

One or more baskets 17 can be used within the vessel 15 by placing thebaskets 17 through the opening. FIG. 3 is a side view of the separationsystem of FIG. 1 with an additional basket, in accordance with onembodiment. When multiple baskets are used, the baskets 17, 42 can benested together within the vessel 15 to increase a selectivity of theseparation that will occur. The different baskets may have differentdiameters of mesh as to isolate plant particulates of varying size. Forexample, the more baskets used, the more likely the desired componentis, by itself, separated from the remaining plant material. Each basket17 can be made from a mesh material, such as stainless steel, with adiameter of open space, between grids of the mesh material, between10-10,000 microns. The diameter of the mesh material and the number ofbaskets used can be based on the desired plant material to be processedor the desired plant component to be separated, as well as a desiredlevel of separation. Additionally, a width of the mesh grids can be inthe range of 25-400 um; however, in one embodiment a size of 305 um isused. Other sizes of the mesh diameter and grid width are possible, aswell as other types of mesh material. At a minimum, the material for thebasket 17 should be able to withstand temperatures at or below −150degrees Celsius. A shape of the baskets can be tapered on a bottom endand include at least one handle or attachment point for use duringinsertion and removal of the basket from the vessel.

Returning to the discussion with reference to FIG. 2 , during theseparation process, a lid 11 can be placed over the top opening of thevessel 15. The agitator 20 can be affixed to the bottom side of the lid11, facing inside of the vessel, and can be powered manually or via amotor 12, which can be affixed to a top side of the lid 11. The agitator20 can include a shaft 13 that extends from the bottom side of the lidand extends downward. One or more paddles 14 are affixed on one end ofthe shaft 13, opposite the lid 11. The paddles 14 are each shaped as oneof a rectangle, square, triangle, oval, or trapezoid, however, otherpaddle shapes are possible. The paddles 14 can have the same shape andsize, or different shapes and sizes. Additionally, in one embodiment,one or more of the paddles can be perforated with holes of varyingcircumference.

A length of the agitator shaft 13 is dependent on a depth of the vessel15 and any baskets 17 placed into the vessel. Additionally, the paddleshape and size is dependent on a diameter of the inside of the vessel.At a minimum, the paddles 14 should conformably fit within the vesseland any baskets 17 placed within the vessel. Preferably, the paddlesextend from the shaft to a point just short of an inside wall of thebasket to prevent obstruction of the paddles during agitation.

The agitator facilitates separation of plant material placed into thevessel. FIG. 2 is a flow diagram showing a method for separating plantmaterial via the separation system of FIG. 1 . The jacket surrounding atleast a portion of the vessel is either filled with an insulator orvoided with a vacuum. In one embodiment, the jacket is placed (block 31)under a vacuum in the range of 759 torr down to the minimum pressurerating of the vessel. Next, upon ensuring the valve is in a closedposition, the vessel is filled (block 32) with cryogenic fluid to apredefined mark. In one embodiment, the fill mark can be determined toprevent spilling of the cryogenic fluid out of the vessel due todisplacement by a basket and plant material.

The cryogenic fluid can include helium, hydrogen, nitrogen, neon, air,oxygen, fluorine, argon, methane, or a combination of such fluids.Additionally, other types of cryogenic fluids are possible. At aminimum, the cryogenic fluid should be at or below −150 degrees Celsius.In one embodiment, liquid nitrogen is used.

Plant material is placed (block 33) in at least one basket that islowered (block 34) into the cryogenic fluid though the opening in thevessel. The plant material can include whole plants, flowers, trimmings,leaves, stalks, roots, or stems, as well as any other plant parts. Anamount of the plant material to be placed in the vessel is dependent ona size of the vessel. In one embodiment, up to 3,000 grams of plantmaterial can be processed at a single time; however, other amounts arepossible. Prior to placement in the basket, the plant material is frozenand subsequently pulverized. In one embodiment, the plant material isrecently harvested to prevent drying of the plant and maximizepreservation of desired plant components and other chemical compoundswithin the plant material.

Once the basket is positioned in the vessel, the lid is placed on thevessel and the agitator provides (block 35) agitation to the plantmaterial by spinning the paddles within the basket, which results inseparation of particular components from the plant material. Theagitation can occur manually or via a motor. The environment inside thevessel, provided by the cryogenic liquid, helps solidify certain plantparticulates, such as indumentums, and makes those particulates easilyseparable from the plant material, such as by reducing rupture due tothe agitation and force of separation. Additional baskets with varyingsizes of mesh can be used to separate different plant components bysize.

The agitation should be performed for a time period long enough tosufficiently separate a desired component, such as between one and 60minutes, and at a speed fast enough to ensure full agitation of theplant material within the cryogenic fluid. In one embodiment, theagitation time should be between 10 and 15 minutes.

Upon completion of the agitation, the lid is removed and the basket,with any remaining plant material, is raised (block 36) above thecryogenic fluid for draining. The plant particulates can be allowed tosettle to the bottom of the vessel, in or near the tapered stem areaabove the valve, over the course of 1-30 minutes. However, other timesare possible, such as over 30 minutes. The valve is then moved (block37) to an open position to allow the separated plant particulate to exitthe vessel onto the collection tray via the cryogenic fluid. In oneembodiment, the valve can be toggled between open and close positions torelease a minimum volume of cryogenic fluid to fully empty the separatedplant particulate. Once clean fluid flows, the valve is closed. Theseparated plant particulate, upon removal from the vessel, can have awater content up to 90% and can be dried to a desired concentrationusing, for example, a freeze dryer. However, other drying methods arepossible.

An amount of drying can be based on the separated plant particulate. Inone embodiment, drying should occur until the plant particulate has amoisture content of less than 10%. Additionally, refinement of theseparated plant particulate can be performed prior to or after drying.Refinement can occur via by passing the separated plant particulatethough additional sieves or screens to isolate target plant components,performing a solvent extraction of the separated plant particulate,steaming the plant particulate, or performing a vacuum distillation. Theseparation process can be repeated using the same cryogenic fluid withnew plant material.

Once separations have been completed, the vessel and all other partsshould be cleaned. Due to the vessel design, cleaning is easilyperformed and can reduce the time necessary between the separation ofdifferent plant materials, which increases the amount of plant materialprocessed during a particular time period. Also, the lack of pumps andtubing, as well as the lack of water, helps prevent the introduction ofmicrobial contamination.

In one example, cannabis has thermolabile compounds, which are mosthighly concentrated in the indumentums of the cannabis plant. As part ofthe separation process, the cannabis plants are frozen, pulverized, andplaced in a basket with a mesh grid having a size of 305 um. The basketand cannabis plants are lowered into the cryogenic fluid. For instance,3,000 g of cannabis can be processed at a time. Manual agitation can beperformed for 12 minutes, after which the basket is removed from thecryogenic fluid and drained. The valve is released and the indumentums,which were separated from the cannabis plant during agitation, arereleased from the vessel. The indumentums are then placed in a freezedryer for 18 hours.

In a further embodiment, a recirculating pump 41, as shown in FIG. 3 ,can be installed on a bottom of the vessel. The recirculating pump 41can pump liquid from the bottom of the vessel to the top of the vessel,such as to a predefined mark or liquid line inside the vessel.Recirculating the liquid in the vessel creates a circular downward flow,which facilitates filtration.

While the invention has been particularly shown and described asreferenced to the embodiments thereof, those skilled in the art willunderstand that the foregoing and other changes in form and detail maybe made therein without departing from the spirit and scope.

What is claimed is:
 1. A method of cryogenic separation of plantmaterial, the method comprising: a) placing a sieve into a vessel; b)placing plant material into the sieve; c) providing cryogenic fluid ator below −150 degrees Celsius to the sieve; d) agitating the plantmaterial within the sieve and the vessel to separate plant particulatessolidified by the cryogenic fluid from a remainder of the plantmaterial; and e) removing the cryogenic fluid and plant particulatesfrom the vessel.
 2. The method of claim 1, wherein the sieve includes amesh portion.
 3. The method of claim 2, wherein the sieve is a basket.4. The method of claim 3, wherein step (e) comprises opening a valve. 5.The method of claim 1, wherein step (e) comprises opening a valve. 6.The method of claim 1, wherein step (d) is performed by an agitatorcomprising a shaft and at least one paddle at an end of the shaft. 7.The method of claim 6, wherein step (d) includes spinning the at leastone paddle within the sieve.
 8. The method of claim 1, wherein thecryogenic fluid comprises liquid nitrogen.
 9. The method of claim 1, themethod comprising: before step (e), allowing the plant particulates tosettle near an outlet of the vessel.
 10. The method of claim 9, whereinoutlet is near a tapered stem area.
 11. The method of claim 1, themethod comprising: placing a jacket around at least a portion of thevessel; and performing at least one of: filling the jacket with aninsulator; and voiding the jacket with a vacuum.
 12. The method of claim1, the method comprising: pulverizing the plant material prior toplacement in the vessel; and freezing the plant material prior toplacement in the vessel.
 13. The method of claim 1, wherein the sieveincludes a lid.
 14. The method of claim 1, the method furthercomprising: placing a second sieve in the vessel below the sieve; andproviding cryogenic fluid at or below −150 degrees Celsius to the secondsieve.
 15. The method of claim 14, wherein the sieve and the secondsieve each include a mesh portion.
 16. The method of claim 15, whereinthe mesh portion of the sieve has a first mesh size, and the meshportion of the second sieve has a second mesh size different from thefirst mesh size.
 17. The method of claim 1, the method comprising:providing a collection tray below the sieve.
 18. The method of claim 17,the method comprising: collecting the plant particulates in thecollection tray.
 19. The method of claim 1, the method comprising:freezing the plant material prior to placement in the sieve.
 20. Themethod of claim 1, the method comprising: recirculating the cryogenicfluid within the vessel.